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Increased production in high water-cut field a challenge

An operator in southeast Asia wanted to reverse declining production from an old field where production is currently driven by waterfloods and most of the wells have ESPs.

Water cut in the field is in the range of 85%–99%, and wells are constantly being worked over. Zones with high water cut are squeezed off while other zones are reperforated. Further, many of the thinly laminated sand layers have proved difficult to produce because of nearwellbore damage.

The operator invited Schlumberger to initiate a project to determine the best solution for increasing production.

Postperforating propellant pulse selected to fracture the near-wellbore area

The first step in the field trials was reperforating two wells with PowerJet Omega deep penetrating charges, resulting in productivity increases of 200% and 325%—from 150 bbl/d to 450 bbl/d in the first well and from 150 bbl/d to 640 bbl/d in the second well. Flow rates were stable throughout the first 30 days of production.

To further improve productivity, the operator decided to fracture the near-wellbore area with a postperforation propellent pulse. The propellent pulse system effectively treats intervals by combining a solid propellant with an ignition device that controls the burn radially inward.

Because the propellant burns very rapidly instead of detonating like an explosive, the generated pressure pulse is powerful enough to fracture the formation without damaging the casing or adjacent plugs or packers. This feature enables precise treatment of intervals that would not be reached by a standard hydraulic fracturing job, warranting consideration of the propellent pulse system for the desired near-wellbore treatments.

Based on well and formation parameters and the design of the propellent pulse toolstring, propellent pulse planner software was used to design a job that would produce a 2,500-psi pressure pulse to create near-wellbore fractures.

Flow rates doubled in both test wells

Thirty days after they had been perforated with PowerJet Omega charges, the two test wells were killed and the completions were pulled. The postperforating propellent system was then run, and the pressure pulse was recorded by a fast gauge at the bottom of the string. Gauge data confirmed that the peak pressure was close to the planner software estimate of 2,500 psi.

Swab testing showed good improvement in productivity. When the wells were put back on production, the productivity index increased 3 times in the first well and 25 times in the second. Flow rates roughly doubled in both wells to 950 bbl/d and to 1,150 bbl/d, respectively.

The tests confirmed that the postperforation propellent system could be an effective nearwellbore stimulation tool, enabling skin to be bypassed and productivity to be improved in the field.